Evolutionary trajectories of ultra-compact "black widow" pulsars with very low mass companions

TL;DR

This paper models the detailed evolution of ultra-compact 'black widow' pulsars with very low mass companions, revealing new evolutionary paths that explain observed systems and considering alternative exotic companion scenarios.

Contribution

It introduces a comprehensive binary evolution model including mass transfer, evaporation, and irradiation effects, demonstrating a new evolutionary pathway for ultra-compact pulsar systems.

Findings

Identifies a new evolutionary path for black widow pulsars.

Explains observed short-period systems with compact donors.

Suggests possible exotic nature of some low-mass companions.

Abstract

The existence of millisecond pulsars with planet-mass companions (Bailes et al., 2011) in close orbits is challenging from the stellar evolution point of view. We calculate in detail the evolution of binary systems self-consistently, including mass transfer, evaporation and irradiation of the donor by X-rays feedback, demonstrating the existence of a new evolutionary path leading to short periods and compact donors as required by the observations of PSR J1719-1438. We also point out the alternative of an exotic nature of the companion planet-mass star.